A disc-type recording medium (in the following, called an “optical disc”), to which optical reading is applied, such as a DVD (Digital Versatile Disk), a CD (Compact Disk), etc., has rapidly become widespread for use in storing computer files and moving-image streams. An optical disc has a large storage capacity and is capable of random accessing. Also, unlike a contact-type magnetic recording medium, there is no concern for abrasion and damage on the recording face by reading, head crash, etc. Also, the disc surface is strong, and there is low risk of accidental data loss. In recent years, optical discs are widely used also for external recording media and external storage devices for computers.
A disc-type recording medium is capable of random accessing, and thus in the case of recording an AV stream, it is possible to find a favorite scene efficiently. At the same time, data is accessed in a non-contact manner, and thus it is possible to use the medium without deterioration.
Also, recently, with an increase in a recording capacity of a disc-type recording medium, video cameras of a type which store moving images into a disc have appeared in place of a known recording tape (for example, refer to Patent Document 1). For example, DVD video cameras have gained users expanding year by year since their appearance on the market in 2000 because of the excellence in image quality and user friendliness, for example having the capability of editing.
For example, in moving image data, a data block to be a unit which requires being played with assurance of a continuous synchronous play, namely a real-time play, constitutes one clip (Clip), which is recorded as one moving image file. With a moving-image play list (MoviePlayList), it is possible to specify individual play start points (IN points) and play end points (OUT points) for one or more clips to specify play sections and a play sequence of the moving image data. Also, it is possible to freely set reference relationships between clips and play lists. For example, it is possible to make a reference to a certain clip from two play lists having different IN points and OUT points. Furthermore, it is possible to freely set reference relationships between titles and moving image objects.
A moving-image play list is specified by a navigation command in a moving image object (MovieObject) to be played. A reference to a moving image object is listed in an index table as an entry of a title. The index table is the data read first when a recording medium is loaded into a player, and the user can view the titles described in the index table.
Here, on a large capacity recording medium of next generation type, for recording purposes, in consideration of user's convenience, it is desirable to enable the user to divide a moving image clip captured by a video camera into parts for each play section, and to perform editing, such as rearrangement of the parts on a recording medium, or deletion of a part of the parts. At the same time, there are requests to take out a recording medium, on which recording and edit operation have been performed, from a recording device, such as a video camera at any time, and to load the medium into a playback-only apparatus to view the captured moving image on a TV monitor.
In AVCHD (Advanced Video Coding High Definition), which is a standard mainly targeted for applications for a video camera, a determination is made on the design of the specification, such as on the data format for a high-definition (HD) video camera by adding functions of recording compatibility and recordable compatibility. Here, it is thought that it is necessary to define edit operations on a medium while maintaining the compatibility of a recording medium between a video camera and playback-only devices.
Also, rearrangement editing of contents include non-destructive editing in which only the positions of parts referenced on a play list viewed by the user are rearranged and the stream data on a recording medium is not edited, and destructive editing in which the positions of the parts themselves on a recording medium are rearranged. In the latter case, there is a problem with a stream format.
If two AV streams are continuously played back over the boundary, the internal buffer held by the decoder might overflow. Usually, the playback of a prior stream is terminated once, and then the next stream is played back. Thus, a screen freezes for a moment at the time of changing streams. In order to cope with this, it is possible to perform “seamless playback”, which continuously plays back over streams, by encoding so that a predetermined buffer model is not broken down.
For an AVCHD stream file format, the MPEG (Moving Picture Experts Group)-2 system has been already determined. A MPEG2-TS (Transport Stream) stream does not cause a decoder to lose data at data playback time as long as the stream conforms to a predetermined MPEG buffer model, and thus seamless playback is possible. However, if streams are subjected to rearrangement editing by non-destructive editing, the connection condition allowing seamless playback is not met any longer between a prior part and a succeeding part. Thus, a defective image is output at the connection part at stream playback time.
Patent Document 1
Japanese Unexamined Patent Application Publication No. 2004-120364